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Panics when parsing a single hyphen #410

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cite-reader opened this issue Feb 3, 2016 · 4 comments
Closed

Panics when parsing a single hyphen #410

cite-reader opened this issue Feb 3, 2016 · 4 comments
Labels
A-parsing Area: Parser's logic and needs it changed somehow. C-bug Category: Updating dependencies

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@cite-reader
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Given the following minimal test case:

[package]
name = "repro"
version = "0.1.0"

[dependencies]
clap = "2.0.2"
extern crate clap;

fn main() {
    clap::App::new("repro").get_matches();
}

running the resulting executable as ./target/debug/repro - produces the error thread '<main>' panicked at 'index out of bounds: the len is 1 but the index is 1', /home/cite-reader/.multirust/toolchains/stable/cargo/registry/src/github.com-88ac128001ac3a9a/clap-2.0.2/src/osstringext.rs:42.

Running with RUST_BACKTRACE=1 additionally produces this wall of text:

stack backtrace:
   1:     0x55d96739e470 - sys::backtrace::tracing::imp::write::haa19c02b4de52f3bG0t
   2:     0x55d9673a07a5 - panicking::log_panic::_<closure>::closure.41218
   3:     0x55d9673a0220 - panicking::log_panic::h527fe484e9de8fe1W7x
   4:     0x55d9673961a3 - sys_common::unwind::begin_unwind_inner::h51f64b1a34c60827fTs
   5:     0x55d967396538 - sys_common::unwind::begin_unwind_fmt::h0845853a1913f45blSs
   6:     0x55d96739dad1 - rust_begin_unwind
   7:     0x55d9673ccf2f - panicking::panic_fmt::h3967afc085fe8067LFK
   8:     0x55d9673cd0a2 - panicking::panic_bounds_check::h3ef0001c29fc27faREK
   9:     0x55d9673120ef - osstringext::_<impl>::starts_with::h26506bceadbe96d4Gkj
                        at /home/cite-reader/.multirust/toolchains/stable/cargo/registry/src/github.com-88ac128001ac3a9a/clap-2.0.2/src/osstringext.rs:42
  10:     0x55d967309837 - app::parser::_<impl>::get_matches_with::h2749516486128734984
                        at /home/cite-reader/.multirust/toolchains/stable/cargo/registry/src/github.com-88ac128001ac3a9a/clap-2.0.2/src/app/parser.rs:475
  11:     0x55d967307ed3 - app::_<impl>::get_matches_from_safe_borrow::h15298357069185562126
                        at /home/cite-reader/.multirust/toolchains/stable/cargo/registry/src/github.com-88ac128001ac3a9a/clap-2.0.2/src/app/mod.rs:788
  12:     0x55d967305b9f - app::_<impl>::get_matches_from::h16246934518760431591
                        at /home/cite-reader/.multirust/toolchains/stable/cargo/registry/src/github.com-88ac128001ac3a9a/clap-2.0.2/src/app/mod.rs:700
  13:     0x55d967305a9d - app::_<impl>::get_matches::h2e07d26000a6a67e1xf
                        at /home/cite-reader/.multirust/toolchains/stable/cargo/registry/src/github.com-88ac128001ac3a9a/clap-2.0.2/src/app/mod.rs:653
  14:     0x55d9672af440 - main::h3ed4f383bb959950faa
                        at src/main.rs:4
  15:     0x55d96739ffc4 - sys_common::unwind::try::try_fn::h11901883998771707766
  16:     0x55d96739d918 - __rust_try
  17:     0x55d96739fc66 - rt::lang_start::hc150f651dd2af18b44x
  18:     0x55d9672b2339 - main
  19:     0x7f67d556360f - __libc_start_main
  20:     0x55d9672af2e8 - _start
  21:                0x0 - <unknown>
@cite-reader
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Is there a reason that starts_with method isn't just the following?

fn starts_with(&self, s: &[u8]) -> bool {
    self.as_bytes().starts_with(s)
}

@kbknapp
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kbknapp commented Feb 3, 2016

Thanks for taking the time to file this! I see you pushed a commit to your fork, feel free to submit the PR!

@kbknapp kbknapp added C-bug Category: Updating dependencies P2: need to have A-parsing Area: Parser's logic and needs it changed somehow. labels Feb 3, 2016
@kbknapp
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kbknapp commented Feb 3, 2016

@cite-reader Also, your commit message is excellent! This is one of many things I need to work harder on (read, "actually do").

@cite-reader cite-reader mentioned this issue Feb 3, 2016
Merged
homu added a commit that referenced this issue Feb 4, 2016
@homu
Auto merge of #411 - cite-reader:hyphen-doesnt-panic, r=kbknapp
1ede878 
fix: Stop lonely hyphens from causing panic

The method `starts_with` as implemented for the `OsStrExt2` trait on
`OsStr` assumed that the needle given is shorter than the haystack. When
this is not the case, the method panics due to an attempted
out-of-bounds access on the byte representation of `self`. Problematic
if, say, an end-user gives us `"-"` and the library tries to see if that
starts with `"--"`.

Fortunately, slices already implement a `starts_with` method, and we can
delegate to it.

This *does* create a semantics change: if both `self` and the needle
have length 0, this implementation will return `true`, but the old
implementation would return `false`. Based on the test suite still
passing, acknowledging the vacuous truth doesn't seem to cause any
problems.

Fixes #410
homu added a commit that referenced this issue Feb 4, 2016
@homu
Auto merge of #411 - cite-reader:hyphen-doesnt-panic, r=kbknapp
355a5fd 
fix: Stop lonely hyphens from causing panic

The method `starts_with` as implemented for the `OsStrExt2` trait on
`OsStr` assumed that the needle given is shorter than the haystack. When
this is not the case, the method panics due to an attempted
out-of-bounds access on the byte representation of `self`. Problematic
if, say, an end-user gives us `"-"` and the library tries to see if that
starts with `"--"`.

Fortunately, slices already implement a `starts_with` method, and we can
delegate to it.

This *does* create a semantics change: if both `self` and the needle
have length 0, this implementation will return `true`, but the old
implementation would return `false`. Based on the test suite still
passing, acknowledging the vacuous truth doesn't seem to cause any
problems.

Fixes #410
@homu homu closed this as completed in #411 Feb 4, 2016
@kbknapp
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kbknapp commented Feb 4, 2016

once #413 merges I'll put out the new version on crates.io

That PR also adds tests so we shouldn't run into this issue again.

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@cite-reader @kbknapp